Anorexia nervosa (AN) is a serious mental illness characterized by significant morbidity and mortality. Yet, there is little evidence to guide treatment, particularly for older adolescents and adults, who comprise the majority of patients. Thus the overall objective of the work described in this application is to develop and evaluate the preliminary efficacy of a new psychotherapeutic intervention for older adolescents and adults with AN. Emotional Acceptance Behavior Therapy (EABT) for AN is based on a research informed conceptualization of AN that emphasizes the role of anorexic behaviors in helping patients avoid negative emotional states that are perceived as overwhelming and intolerable. The intervention incorporates behavioral principles to promote restoration of adequate nutrition and an acceptable body weight, and strategies to increase emotional awareness and reduce the emotional avoidance that perpetuates AN. Two phases of treatment development are proposed. First, the investigators will draft a treatment manual and adherence measure, and pre-test the intervention with 6-8 patients. In the second phase, the preliminary efficacy of EABT will be evaluated by treating 30 AN patients age >17 years in an open 22 week trial. Participants will be assessed at baseline, post-treatment and 3- and 6- months after treatment. It is hypothesized that EABT will be associated acceptable rates of client satisfaction and treatment attrition, and improvements in eating disorder symptoms, other psychiatric symptoms, emotional avoidance, and quality of life at post-treatment. It also is hypothesized that EABT will be associated with improvements in eating disorder symptoms, other psychiatric symptoms, emotional avoidance, and quality of life at 3- and 6-month post- treatment follow-up. If hypotheses are confirmed, the investigators will propose a full-scale randomized controlled trial of EABT in a subsequent application. The proposed work is significant as an effort to develop and systematically evaluate the acceptability and preliminary efficacy of a novel, theory-driven outpatient psychotherapeutic intervention for older adolescents and adults with AN. Findings may lead to an efficacious treatment for AN, a critical public health problem.